import threading

class SessionManager:
    def __init__(self, sess):
        self.sess = sess
        self._lock = threading.Lock()
        self._count = 0

    def start(self):
        with self._lock:
            if self._count == 0:
                self.sess.start(0)  # kontinuierlich
            self._count += 1

    def stop(self):
        with self._lock:
            if self._count > 0:
                self._count -= 1
                if self._count == 0:
                    self.sess.end()